[symfony] File structure explained

http://www.symfony-project.com/book/trunk/file_structure

// root directory structure
'sf_cache_dir_name'   => 'cache',
'sf_log_dir_name'     => 'log',
'sf_lib_dir_name'     => 'lib',
'sf_model_dir_name'   => 'model',
'sf_web_dir_name'     => 'web',
'sf_data_dir_name'    => 'data',
'sf_config_dir_name'  => 'config',
'sf_apps_dir_name'    => 'apps',
 
// global directory structure
'sf_app_dir'        => $sf_root_dir.DIRECTORY_SEPARATOR.'apps'.DIRECTORY_SEPARATOR.$sf_app,
'sf_model_dir'      => $sf_root_dir.DIRECTORY_SEPARATOR.'model',
'sf_lib_dir'        => $sf_root_dir.DIRECTORY_SEPARATOR.'lib',
'sf_web_dir'        => $sf_root_dir.DIRECTORY_SEPARATOR.'web',
'sf_upload_dir'     => $sf_root_dir.DIRECTORY_SEPARATOR.'web'.DIRECTORY_SEPARATOR.'uploads',
'sf_base_cache_dir' => $sf_root_dir.DIRECTORY_SEPARATOR.'cache'.DIRECTORY_SEPARATOR.$sf_app,
'sf_cache_dir'      => $sf_root_dir.DIRECTORY_SEPARATOR.'cache'.DIRECTORY_SEPARATOR.$sf_app.DIRECTORY_SEPARATOR.$sf_environment,
'sf_log_dir'        => $sf_root_dir.DIRECTORY_SEPARATOR.'log',
'sf_data_dir'       => $sf_root_dir.DIRECTORY_SEPARATOR.'data',
'sf_config_dir'     => $sf_root_dir.DIRECTORY_SEPARATOR.'config',